The present invention relates to an embedded magnet type motor.
Conventionally, a rotor core of an embedded magnet type motor has a plurality of accommodation holes aligned in the circumferential direction, and the accommodation holes perforate through the rotor core axially. In the accommodation holes, magnets are accommodated.
In the embedded magnet type motor disclosed in Japanese Laid-Open Patent Publication No. 2005-51982, each of a plurality of magnetic poles includes a pair of magnets arranged in a V shape to protrude radially inward. Specifically, when the number of magnetic poles of the embedded magnet type motor is P, the number of magnets is 2 P. With this construction, a higher torque can be realized in comparison with a motor in which one magnet is provided per one magnetic pole.
However, when two magnets are provided per one magnetic pole, the number of parts increases and parts management cost and assembly cost also increase.
In the embedded magnet type motor of the publication described above, an outer bridge is formed between the radially outer end of each accommodation hole for accommodating a magnet and the outer peripheral surface of the rotor core. Two outer bridges are provided per one magnetic pole. Therefore, leakage fluxes passing through the outer bridges are excessive as a whole of the motor. This reduces the effective fluxes of the embedded magnet type motor and obstructs the torque increase.